The present invention relates generally to a conveyor, installation, and method for moving articles and, more particularly, for moving articles, such as vehicle bodies, through a series of dip tanks.
Various conveyor systems are available to transport articles such as vehicle bodies through production areas. Of particular interest for the present invention are conveyor systems that move articles, such as vehicle bodies, through a series of dip tanks for treating the vehicle body prior to painting. Conveyor systems of this type are generally required to transport the vehicle body along the path of travel in a manner that supports the vehicle body in a variety of orientations relative to gravity, permit the lowering and raising of the body into and out of the dipping tanks without unduly lengthening the dip tanks, and prevent contaminants from contacting the vehicle body or the solution in which the body is dipped. Cost, space, and maintenance concerns are also important. While many of these concerns are addressed by available conveyor systems, the present invention provides numerous improvements and addresses other deficiencies in the art.
In one conventional system, pairs of pendulums are transported through a conveyor path by two separate and distinct conveyor chain loops. The pendulums have hooked lower ends that are releasably connectable to skids or carriers that support the vehicle body. In order to effectively transport the vehicle through the dipping tanks, the pendulums on each conveyor move in aligned pairs. As the position of the pendulums are fixed to move with its respective separate chain, this alignment is commonly achieved by a drive assembly that engages both of the separate and distinct chains. However, as each chain moves through a separate loop, each chain is subjected to different conveyor components, such as take-ups, lubricators, tracks, rollers for turns, and the like, as well as different tensions. Each of these different components give rise, both individually and in combination, to different stresses and generate differing forces that tend to deteriorate the separate chains over time. These forces in turn cause chain wear, such as a narrowing of the diameter of chain pins that intercouple adjacent links as well as a broadening of the pin passages in the chain links. Ultimately, the length of each chain changes at a different rate over the operational life of each conveyor. As the length of each chain changes, the pendulums tend to become misaligned.
A further disadvantage of the two conveyor system described above is the need for two separate return paths between the point that the vehicle bodies are unloaded and loaded. Due to the nature of the dipping environment, the pendulums are preferably passed through a cleaning station during the return path. With two separate return paths, one on each side of the travel path of the vehicle bodies, two separate cleaning stations are required.
Yet still another disadvantage of the prior art system described above is the inability of the separate conveyors to transport the vehicle body around horizontal turns. Due to space constraints and the length of the required dipping lines, it is common to have two or more parallel treatment paths through which each vehicle must pass. Without the ability to traverse horizontal turns, this prior art system, and other available prior art systems, require the vehicle body to be unloaded from the pendulums at the end of the first line, rotated 90 degrees, moved transversely into alignment with the second line, rotated an additional 90 degrees, and loaded onto the pendulums of the second pair of conveyors. The unloading from the first line, rotation, horizontal displacement, further rotation, and loading onto the second line requires a complex and expensive array of lifts, turntables, and roller tables. All of these components are required simply because existing pendulum conveyor systems cannot transport the vehicle bodies around horizontal curves. Accordingly, a pendulum conveyor system capable of transporting an article, such as a vehicle body, through the treatment areas as well as horizontal curves would greatly simplify the transporting operation and result in significant cost savings.
The inability of prior art systems to traverse horizontal curves results in part from the chording of the spaced pendulums on each conveyor and the need to maintain alignment of the pendulum pairs. More particularly, the pendulums coupled to the front and rear of the vehicle carrier are spaced at a predetermined distance from one another and fixed to move with the conveyor chains. This spacing creates a chordal distance between adjacent pendulums on each of the spaced and separate chains that cannot be effectively accommodated in a horizontal turn. Moreover, while the spaced conveyors must move at the same speed in straight sections to maintain pendulum alignment, as the arc length of the inner and outer conveyors differ in a horizontal turn, the outer conveyor must move at a greater speed than the inner conveyor during the turn.